The traditional implantable cardiac pacemaker includes a pulse generator device to which one or more flexible elongate lead wires are coupled. The device is typically implanted in a subcutaneous pocket, remote from the heart, and each of the one or more lead wires extends therefrom to a corresponding electrode, coupled thereto and positioned at a pacing site, either endocardial or epicardial. Mechanical complications and/or MRI compatibility issues, which are sometimes associated with elongate lead wires and well known to those skilled in the art, have motivated the development of implantable cardiac pacing devices that are wholly contained within a relatively compact package for implant in close proximity to the pacing site, for example, within the right ventricle RV of the heart. With reference to FIG. 1A, such a device 30 is illustrated, wherein an hermetically sealed housing 36, preferably formed from a biocompatible and biostable metal such as titanium, contains an electronic controller and associated power source (not shown), to which at least one electrode 31 is coupled, for example, by a hermetic feedthrough assembly (not shown) like those known to those skilled in the. Housing 36 may be overlaid with an insulative layer, for example, medical grade polyurethane, parylene, or silicone, and a portion of the insulation layer may be removed to form another electrode 32, for example, to provide bipolar pacing and sensing in conjunction with electrode 31.
FIG. 1A shows device 30 having been delivered to an implant site by an operator, via a standard guiding catheter 150 known to those skilled in the art, which the operator has maneuvered up through the inferior vena cava IVC and across the right atrium RA into the right ventricle RV. The delivered device 30 is shown fixed at the implant site by a fixation member 35 thereof. Although catheter 150 may be suitable in the illustrated instance, there is a need for more versatile types of catheters capable of delivering implantable medical devices, like device 30, to some alternative implant sites, for example, like a site S of FIG. 1A, located on a septal wall of the right ventricle RV.